Warner Bros. put $50 million into Syriana and allowed writer-director Stephen Gaghan as much time and travel as necessary to research and write his story. The company would be well advised to pony up a few extra bucks to provide film-goers with a flow chart that connects the myriad scattered dots that make up this movie about the high price of oil. So dense and complex is its story, and so varied and vast are its characters and settings, that viewers will not make much sense of it the first time around. Which is not to suggest it's an impossible or unbearable task -- merely that you should prepare yourself.

My notepad is filled not with the usual critical scribblings about noteworthy scenes and remarkable performances, but instead with detailed notes about the dark doings of Syriana's endless buffet of protagonists: the weary, disillusioned C.I.A. agent (George Clooney) betrayed by his bosses for seemingly capricious reasons; the slick energy analyst (Matt Damon) who parlays the death of his six-year-old son into a gig working for a prince (Alexander Siddig) promising reform in his unnamed Middle Eastern country; the Washington attorney (Jeffrey Wright) who will screw whomever necessary to clear the way for a merger between two petrochemical corporations; the sympathetically portrayed Pakistani oil-field worker (Mazhar Munir) lured into terrorism when tossed out of his job; and the various other government spooks and Middle Eastern emirs and Texas oilmen and Justice Department cronies and well-connected lawyers who flesh out this meaty tale. Only much later does one stop to consider the flinty camerawork, the impatient editing (which tends to end scenes abruptly, almost arbitrarily) and the tense score -- the things that make this a movie, not merely a treatise on global politics.

Syriana plays much like the film for which Gaghan won his screenwriting Oscar, Traffic: Storylines and characters criss and cross, intersecting at various points without ever fathoming the connections. Syriana demands your attention and patience, but it's no different than the video game that leaps from level one to level ten in order to explain its point; Gaghan's a filmmaker for the gamer who doesn't need to have the plot follow a neat, linear path. Besides, you don't need to know precisely what's going on; no one else in the film does, either. Which is Gaghan's point: These people who are making a killing in the oil biz believe they know everything, control everything, are everything -- but even the kings are mere pawns on the sandy chess board. The ruler is just as suddenly the slave, the underling just as quickly the boss. There is but one master: oil itself.

Gaghan based his tale on See No Evil, the riveting 2001 book written by former C.I.A. operative Robert Baer, upon whom Clooney's Bob Barnes is based. Like Baer, Barnes is cast aside by the agency after an assassination attempt goes awry and he's forced to take the fall. (Clooney, obscured by a thickly tangled beard and a pale, paunchy gut, suffers much worse in a torture scene that led to a real-life spinal injury; it's harrowing to watch on many levels.) Yet Syriana plays more like an adaptation of Baer's 2004 book Sleeping With the Devil: How Washington Sold Our Soul for Saudi Crude, which portrays the U.S. government as a betrayed but forgiving whore with its "eye on [the Middle East's] bulging wallet lit by the moonlight on the dresser." Baer and his acolyte Gaghan infuse their work with a vitality lit by anger, sadness and frustration; in their narratives, there are no heroes or saviors, only the culpable and the corrupt.

In Syriana, Barnes is the closest we come to a "good guy," and he's an acknowledged assassin; when first we see him, he's walking away from an exploding car that contains a terrorist and the missile launcher Barnes just sold him. Everyone else is knee-deep in moral quicksand, especially Damon's Bryan Woodman, whose wife (Amanda Peet) comes to find his actions so reprehensible she can no longer look at him, and Wright's Bennett Holiday as the attorney only too happy to give "the illusion of due diligence" as he begins to betray even his bosses.

You will not always know why someone's doing what he's doing; motives, if mentioned at all, are rarely offered in loud pronouncements, but as hushed whispers and slight nods of the head. Characters speak in the knowing aphorisms of the indignantly self-righteous or the tragically damned. "Corruption keeps us safe and warmCorruption is why we win," says Tim Blake Nelson as the senator who believes that doing bad is good for business. It's but a matter of time, of course, before he takes the fall. Others are sacrificed, too -- in the name of what, exactly, we're never sure, save the price of doing business.

Yes, Syriana is confusing -- confounding, even -- but it's a provocative, infuriating, beautiful and essential mess worth pondering. Gaghan, whose sole other directorial credit is his dreary thriller Abandon with Katie Holmes, has matured into some kind of cinematic New Journalist whose fiction resonates with facts he gathered over several years of traveling and note-taking with Baer as his guide. He damns one, he damns all -- including his audience, who just wants cheap gas, no matter what it costs the other guy. Fact is, Syriana may be the best advertisement for a Prius ever made.